Contact brush spreader and guide for electric selector switches



Jan. 31, 1950 G. DEAKIN CONTACT BRUSH SPREADER AND GUIDE FOR ELECTRIC SELECTOR SWITCHES 5 Sheets-$heet 1 Filed July 29, 1944 Fig 1 IN VEN TOR. GERALD DEAK/N AGE/v1 Jan. 31, 1950 G. DEAKIN 2,495,701 CONTACT BRUSH SPREADER AND GUIDE FOR ELECTRIC SELECTOR SWITCHES Filed July 29, 1944 5 Sheets-Sheet 2 Fig 2 INVENTOR. GERALD DEAK/N Jan. 31, 1950 DEAKIN 2,495,701

G. CONTACT BRUSH SPREADER AND GUIDE FOR ELECTRIC SELECTOR SWITCHES Filed July 29, 1944 I 5 Sheets*Sheet 3 Fig 3 INVENTOR. GERALD DEAKIN AGENT Filed July 29, 1944 Jan. 31, 1950 G. DEAKIN 2,495,701

CONTACT BRUSH SPREADER AND GUIDE FOR ELECTRIC SELECTOR SWITCHES 5 Sheets-Sheet 4 Fig 4 INVENTOR. GERALD DEAK/N AGENT Jan. 31, 1950 K N 2,495,701

CONTACT BRUSH SPREADER AND GUIDE FOR ELECTRIC SELECTOR SWITCHES Filed July 29, 1944- 5 Sheets-Sheet 5 I N V EN TOR. GAP/91D D! 1911 //Y AGENT Patented Jan. 31, 1950 CONTACT BRUSH SPREADER AND GUIDE FOR ELECTRIC SELECTOR SWITCHES Gerald Deakin, New York ternational Standard E York, N. Y., a corpora N. Y., assignor to Inlectric Corporation, New tion of Delaware Application July 29, 1944, Serial No. 547,126

My invention relates to selector switches of the kind used in telecommunication systems and more particularly to contact brush devices for such selector switches.

An object of the invention is the provision of a brush unit for a selector switch which may be moved at high speeds with a minimum of vibration over a line of terminal pins of small cross section and which at the same time will make effective rubbing contact with the pins for a maximum period without danger of shortcircuiting adjacent pins or of damage either to the pins or to the brushes themselves.

Another object of the invention is a brush unit which is constructed from a few relatively simple parts and which may be mounted in a brush carriage without the use of special tools or jigs.

The invention has as a still further object the provision of means for spreading the contact brushes to convert from a rubbing to non-rubbing contact. This feature is particularly applicable in a flat type of switch having two sets of brushes which are traversed over a terminal bank with a linear reciprocatory movement, only one and a different set of brushes making rubbing contact with the terminals in each direction of movement.

The above objects and features of my invention will be clearly understood from the accompanying drawings in which:

Fig. 1 is a front elevation of a brush carriage,

Fig. 2 is a section taken on the line 2 -2 of Fig.3,

Fig. 3 is a section taken on the line 3-3 of Fig. 2,

Fig. 4 is a section taken on the line 4-4 of Fig. 2,

Fig. 5 is a section taken on the line 5-5 of Fig. 2 showing the brushes in three difierent positions.

Fig. 6 is a front elevation of a brush guide,

Fig. 7 is a bottom view of the brush guide,

Fig. 8 is an end view of the brush guide, Fig. 9 is a section on the line 9-9 of Fig. 8, and

Fig. 10 shows a detail of a shift bar.

My invention is described as applied to a flattype selector switch of the kind in which the brush carriage is driven by a rotating continuous thread worm as disclosed in my Patent No. 2,330,812, issued October 5, 1943. In the accompanying drawings I have shown for convenience only one half of a brush carriage assembly comprising four brush units. It will be understood 11 Claims. (Cl. 179-27.5)

that any suitable number of brush units may be mounted on a brush carriage.

Referring first to Figs. 1 to 4, a brush unit comprises a punched fiber strip I provided with holes for the passage of pins 2 and to which are secured by rivets or eyelets 3 two outer phosphor bronze springs 4 and two inner brush springs 5. A pair of depending supports 6 for a brush guide 1 is secured to each end of thestrip I. The lower ends of these supports 6 are bent inwardly so as to engage in slots 8 in the guide 1. springs 4 are formed with lateral extensions 9 which are shaped to wipe over the sides of the feeder bars Ill.

The lower ends of the inner brush springs 5 are formed with contact surfaces adapted to wipe over the contact pins II in the contact bank l2. The pins H are made of a hard metal such as phosphor bronze.

The outer and inner brush springs 4 and 5 are straight and in contact for the major portion of their length but near the tip the inner brush spring 5 is bent at an angleto form a space between the tips of the brush springs 4;

and 5 as shown in Fig. 2. At this region the sides, of the inner springs 5 are also bent back as illustrated in Fig. 5. A small block l3 of resilient material such as Neoprene, is positioned in the space between the tips of each pair of brush springs 4 and 5 and is held in position by a lip [4 on the lower edge of the outer spring 4 and by the bent back sides of the spring 5.- Tests have demonstrated that the blocks l3 of soft material eifectively damp vibration of the brushes while in motion. Tests have also shown that blocks l3 reduce by damping the minute mechanical vibrations of the brush while at rest which minute Vibrations are often the cause of the so-called microphonic contact between the brushes and the terminal contacts.

Figs. 6 to 9 show the construction of the brush guide I which comprises a molded Bakelite block formed with slots 8 to accommodate the inturned ends of the supports 6. The center of the block isslotted on both sides where the brushes pass over it to provide a section I5 of reduced thickness which limits the movement of the brushes when they are between terminal pins (Fig. 5). The lower portion of the section N5 of reduced thickness is cut away as at IS. A slot IT, in which the pins ll project and slide, extends the full length of the guide and is outwardly flared at its lower edges, as shown in Figs. 7 to 9. The

-- 5 ends of the slot IT are also flared as shown in The upper portions of the outer brush Fig. 8 in order to guide the pins into the slot as the guide moves over the terminal bank |2.

The brush units are supported in the brush carriage l8, Figs. 1 to 4, by two pins 2 which fit into holes in the four legs of the brush carriag and pass through holes in the ends of fiber strips I. The pins 2 are secured, in the legs of the brush carriage |B by spring clips l9 which slide into grooves formed in the ends of the pins. In the drawings there are illustrated four brush units 4, 5, 6, 9 constituting one half of two sets of four brush units which might in practice be provided on a carriage l8 in a selector switch of the kind in which one set of four brush units makes contact with four rows of terminal pins when th carriage I8 is traversed over the bank in one direction, and the other set of four brush units makes contact with another four rows of terminal pins when the carriage is moved in the reverse direction. Fig. 4 shows the four brush units in the same plane. Fig. 3 shows the elements 4, 5, 5 of two brush units and the elements 9 of the other two units. Fig. 1 shows 4, 5 of two units, 6' of one unit and 9 of three units. The rows of terminal pins II and the brush units of the two sets of four are alternated as shown in Fig. 4. It will be appreciated that any other suitable number of brush units may be provided and that they may be arranged in any desired manner to meet any particular requirements.

In order to prevent short-circuits between brushes, each brush unit is separated from the adjacent one, by a thin sheet of insulating material such as phenol fiber, the pins 2 passing through holes in the sheet.

Means is provided for separating the brushes so that one set of brushes rubs over one set of terminal pins when the brush carriage l8 moves in one direction and the other set of brushes rubs over the other set of terminal pins when the brush carriage moves in the opposite direction. Eight brush separators are employed comprising triangular plates 2i of fiber or other insulating material which are slid between the supports 5 and the inner brush springs 5 of each brush unit. The separator plates 2| are alternately mounted on two pivot pins 22 which pass respectively through the leftand right-hand legs of the brush carriage |8 and through holes in one corner of the plates 2|: the pins 22 are secured in thebrush carriage by spring clips 23. Two further pivot pins 24 pass through holes in the opposite corners of alternate separator plates 21 and through a horizontal shift bar centrally located between the fourth or last unit of one group and the fifth or first brush unit of the second group of four units. To permit the shift bar 25 to be mounted in position after the pivot pins 2, 22 and .24 have been inserted, it is made in two parts 25, 2'! (as shown in Figs. 2, 3, 4 and 10) having oppositely directed slots 28, 29. To assemble the shift bar the two parts 25 and 21 are brought together from above and below the pivot pins 24 the edges of the slots 28, '29 encircling reduced portions 3|! of the pins 24. Two'- phosphor bronze spring clips 3|, Fig. l, are then sprung over the two ends of the bar at the cutaway places 32, Fig. 10, to. hold the two parts. 26, 2'! together. Stop projections 33 are formed on the shift bar parts 25 and 21, one at each end of the carriage Hi, to limit its traverse and thereby the angular movement of the separators 2| which are rocked about pivots 22 by pins 24, when the shift barv 25 ismoved. Ashortdistame above the top of the guide I, the inner springs 5 converge inwardly and over a small part of their length approach one another so that when the tip of the respective separator plate 2| is depressed, the brush springs are spread and forced away from the terminal pins I l, as shown at C, Fig. 5 and in connection with the center brush unit of Fig. 2.

Stop members such as 34, Fig. 1, are mounted on the selector frame 35 at each end of the brush carriage traverse. When, therefore, the brush carriage l8 reaches the right-hand end of the selector and the shift bar 25 engages the p member 34 four of the brush separators 2| are depressed and four are elevated as shown for the two separators in Fig. 1. Those brush separators 2| which are depressed assume the position shown for the middle brush unit in Fig. 2 in which position they engage the converging portions of the inner brush springs 5 and spread the brushes away from the terminal pins II as illustrated at C, Fig. 5. The four brush separators 2| which are elevated assume the position shown for the left-hand brush unit in Fig. 2, thus allowing the brush springs 5 to rub on the pins H as shown at A, Fig. 5, and almost to touch between pins as shown at B, Fig. 5. When the brush carriage |8 reaches the left-hand end of the selector, the shift bar 25 engages a stop similar to 34 and is forced to move in the oppositedirection with respect to the carriage until the projection 33 at the left of the carriage engages the pin 2. The depressed and elevated separators 2| reverse their respective positions thus making the rubbing brushes non-rubbing and the non-rubbing brushes rubbing.

In order that the assembled brush carriage I8 and the selector may be placed on the terminal bank |2 without damage to the brushes or the terminal pins, the brush carriage I8 is moved to one end of the selector as shown in Fig. l. The selector may then be positioned on the bank. and the large flare in the slot I'l at the end of the guide 1 will ensure the guiding of the pins in the slot. The locationof the feeder bars |0 at the opposite end of brush units to the terminal pins permits easy assembly of the brush units in the brush carriage.

It will be observed that the brush supporting strips l are not fixed on the pins 2 but are per-v mitted a certain degree. of, lateral play. The position of brush units is primarily determined by the engagement of the brush extensions 9 with the feeder bars H) but the brush guide 1 plays a very important part. Without it, it would. be impossible to ensure that the pressure and positioning of the brush springs. 5 is thesame on both sides of the terminal pins The brush guide I limits movement of the brush springs 4, 5 when they are between pins and prevents short-- circuits between pins. The ends of the terminal pins II project into the .slot which runs the full length of the guide I. This assures the alignment the brushes with the pins and the accurate making or breaking of contact with the pins as shown in Fig. 5. Although as shown, at B, Fig. 5-, the-brushes almost touch when they are between adjacent terminal pins, it is not possible for themactually to touch since the terminal pins are aligned by the slot I! in guide 1 and the central portion I5 of reduced thickness. in the guide fixes the extent to which the brushescan approach to one another. This reduces vibration during movement and .permits the em-.v ployment of thamaximumrubbing contact which.

in actual practice may be approximately 85 per cent of the distance between pin centers. If the brushes were not so accurately guided by the uide 1, this would be impossible since in case of unequal tension on the brushes that brush having the greater tension would force its way through the space between the pins and short circuit adjacent-pins.

' Since only the ends of the terminal pins enter the slot no part of the guide 7 touches that portion of the surface of the terminal pins l| upon which the brushes rub. This reduces the possibility of small particles of insulating material which may be produced by friction between the guide and the pins collecting on the terminal pins and causing imperfect electrical contact. The slot l1 should be made slightly wider than the diameter of the terminal pins throughout its length so as to provide sufficient clearance to obviate undue wear. Alternatively atthe central region l5 where the brushes pass.

over the guide, the slot may be made about a mil wider than the pin diameter. Since so small a clearance throughout the entire length of the slot might result in undue wear the slot may be widened out on both sides of the region IE to give greater clearance.

Briefly to recapitulate the operation of the selector switch, the terminal bank l2 has terminal pins I projecting in diametrically opposite directions from the two sides thereof forming two flat terminal bank panels in which pins are arranged in rows. With each flat terminal bank a set of selector wipers cooperates, in the present case four wipers with each side. Each wiper consists of an inside spring 5 and an outside spring 4 adapted to be opened and closed as shown in Figs. 2 and 5 to make contact or to clear the row of contact pins II with which the wiper cooperates. The opening and closing of the wiper contacts is in turn controlled by the position of the triangular separator 2|. When the separator is up as shown in Fig. 2 for the left-hand set of contacts, wipers make contact with the terminals, and when the separator 2| is down as shown for the middle set of contacts in Fig. 2, the contacts are cleared by the wiper. Assuming that the separator 2| is up as shown in Fig. 2, the first set of wipers will engage its terminals until the wiper reaches the end of the traverse whereupon its separator 2| will be moved down to spread the wipers and the separator 2| of the adjacent set will be moved up so that, during the return movement of the carriage l8, the second set of Wipers will make contact with the terminals.

Each set of wipers has also contact springs 9 which engage the bus bar I 0.

Finally, each set of wipers is provided with a uide I which travels back and forth with the wipers and engages several contact pins H in the row with which the wipers cooperate. Thus, far more accurate alignment is insured between the contact terminals and the wiper than would be in the case if the wiper were mounted for wiping over a row of terminals without the aid of such long guide or aided by a guide cooperating with some other element of the switch structure than the terminal row proper.

While I have described my invention as applied to a fiat-type selector switch, as will readily be appreciated, it is equally applicable to many other types of switch. Moreover, many modifications will be apparent to those skilled in the art which come within the spirit of my invention, the scope of which is defined in the appended claims. For example, although I have described in detail brush units comprising inner and outer brush springs my invention is equally applicable to arrangements in which the outer brush spring is dispensed with and a single brush spring only is provided. Y

What is claimed is:

1. In a selector switch a terminal bank, a row of contact terminals projecting therefrom, a guide member having a longitudinal slot into which more than three of said contacts project, a movable support, means for mounting said guide member in said support in such manner that it is capable of limited lateral movement in its passage over the'contact terminals, and a pair of brush springs which pass respectively over the two sides of said guide member, said brush springs being mounted on said movable support and having contact surfaces which rub over said contact terminals.

2. A brush assembly according to claim 1 wherein said slot is widened out on both sides of the central portion of the guide member where said brush springs pass over it.

3. In a selector switch a terminal bank, a row of contact terminals projecting therefrom, a movable brush carriage, a brush support, means for mounting said brush support on said brush carriage so that it has a limited freedom of lateral movement with respect to said row of terminals, a guide member having a longitudinal slot into which more than three contact terminals project, means for mounting said guide member on said brush support, and a pair of brush springs mounted on said brush support and extending respectively over the two sides of said member.

4. In a selector switch a terminal bank, a row of contact terminals mounted therein, a movable brush carriage, a brush support comprising a strip of insulating material, a pair of pins passing through the ends of said strip and mounted in said brush carriage, a guide member having a longitudinal slot into which more than three contact terminals project, supporting means for said guide member secured to said strip, and two brush springs mounted on said strip and ex tending respectively over the two sides of said guide member so as to make successive contact with said terminals during the movement of said brush carriage.

5. In a selector switch a terminal bank, a plurality of rows of contact terminals mounted therein, a movable brush carriage, a plurality of brush supporting strips, a pair of pins passing through holes in each respective end of each of said strips and mounted on said brush carriage at right angles to the direction of its movement over said terminal bank, two brush springs mounted on each of said strips, and a guide member supported by each said strip between said brush springs and cooperating therewith and having a longitudinal slot into which more than three contact terminals project.

6. A brush unit assembly for a selector switch comprising a. brush supporting member, a pair of parallel brush springs secured thereto, a contact wiping surface at one end of each spring, a brush guide comprising a block of insulating material positioned between said brush springs, two pairs of depending supports each secured at one end to said brush supporting member and having at the other end an inturned portion which engaged in a slot in said block of insulating material, and a longitudinal slot in the bottom edge oi'said block.

'7. A selector switch. comprising a terminal bank, a row of contact terminals mounted thereon, a brush carriage, a. contact brush mounted on said. brush carriage, means for moving said. brush carriage back. and forth over said terminal bank, means for moving said contact brush alternately into rubbing and non-rubbing relationship with. respect to said contact terminals, and means for actuating said last-mentioned means at the end of each traverse of said brush carriage.

8. A selector switch comprising a terminalbank, two rows of contact terminals mounted thereon, a, brush carriage, two contact brushes mounted on said brush carriage for engagement with the respective rows of terminals, means for moving said brush carriage back and forth over said terminal bank, means for moving said contact brushes alternately into rubbing and non-rubbing relationship with respect to said two rows of terminals in such manner that when one brush is in rubbing relationship the other is in nonrubbing relationship and vice versa, and means for actuating said last mentioned means at the end of each traverse of said brush carriage.

9. A selector switch comprising. a terminal bank, a row of contact terminals mounted thereon, a brush carriage, a contact brush mounted on said brush carriage, means for moving said brush carriage back and forth over said terminal bank, means for moving said contact brush alternately into rubbing and non-rubbing relationship with respect to said contact terminals, a movable shift bar mounted on said brush carriage for actuating said last mentioned means. and a stop member mounted on the switch at each end of the terminal bank in such position as to engage an end of said shift bar at the end of each traverse of said brush carriage.

10. In a selector switch a terminal bank, a row of contact terminals mounted therein, a movable brush supporting member, a pair of parallel brush springs mounted on said brush supporting member, contact surfaces at the ends of said springs for wiping over two sides of said contact terminals, a separator lever member-having two limiting positions and a projection which extends between said brush springs, said springsand said projection being so shapedthat in one limiting position of said lever said contact surfaces are spread out of rubbing engagement with said contact terminals and in the other limiting position they are permitted to. rub over said contact terminals, a pivot on said brush carriage for said separator member, a movable shift bar mounted on said brush carriage, a pivot on. said shift bar for said separator lever member, and a stop member" mounted on the switch at each end of said terminal bank in such position as to engage an end of said shift bar at the end of each traverse of said brush carriage.

11.. A selector switch comprising a terminal bank; a row of contact terminals mounted thereon, a brush carriage, a contact brush mounted on said brush carriage, means for moving said brush carriage back and forth over said terminal bank; means for moving said contact brush alternately into rubbing and non-rubbing relationship with respect to said contact terminals, means for actuating said last mentioned means at the end of each traverse of said brush carriage, a guide member mounted for limited lateral movement on said carriage and in cooperative relationship with said brush for determining the position of said brush when said brush is between two contact terminals and in rubbing relationship therewith, said guide member having portions adapted to cooperate with said contact terminals for aligning said guide member therewith.

GERALD DEAKIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,103,623 Reynolds July 14, 1914 1,249,154 McQuarrie Dec. 4, 1917 1,849,986 Merk Mar. 15, 1932 1,871,358 Butterfield Aug. 9, 1932 2,225,646 Lewis Dec. 24, 1940 2,361,579 Wegenseil Oct. 31, 1944 

